Other then using the Craft Magic Item rules to customize such an item (a lot of work to figure out, mutliple ways and calculations to figure it out, etc.)... Is there any legit way to create a portal and teleportation ring? Any feats or craft skills or magic spells that are out there for such a thing?
If you're looking for point-to-point teleportation, all you need is
teleportation circle (Sor/Wiz 9, Witch 9, Rune 9, Sum 6) and a
permanency spell. That creates a permanent point A to point B portal for 23,500 gp. If you want point B to point A, you have to pay another 23,500 gp to put another one-way portal at point B.
There's a more cost-effective solution, but it's slower and logistically trickier.
Greater create demiplane (Sor/Wiz 9, Witch 9, Cleric/Oracle 9) can be made permanent 22,250 gp, and then you can cast the spell
again, for free, to create a permanent
gate effect between one spot on your demiplane and any one spot on any one plane that you are "very familiar" with-- limited only by the available space within your demiplane. Not only is this cheaper, but it allows you to make interdimensional and interplanetary teleportation networks.
